Wash and peel Jerusalem artichokes; slice.
In covered pan cook in a small amount of boiling salted water till tender, 10 to 15 minutes.
Melt butter in a saucepan; blend in flour, salt, and white pepper.
Add cream or milk all at once.
Cook and stir till thickened and bubbly.
Remove from heat.
Stir in snipped parsley.
Serve sauce over cooked Jerusalem artichokes.